The ultrastructure and cytochemistry of exocrine secretory cells are being studied. Emphasis is being placed upon the basic mechanisms of secretion, with particular attention directed toward the role of the Golgi apparatus and lysosomes in these phenomena. The structure, distribution and cytochemistry of peroxisomes in exocrine glands are also being investigated. The rat parotid gland has been the primary focus of our studies; however, other glands such as the lacrimal, pancreas and thyroid, as well as cultured melanoma cells, are being examined in order to compare them with the parotid gland and to take advantage of cytochemical properties particularly suited for electron microscopy. The biochemistry, ultrastructure and cytochemistry of developing and adult lingual serous (von Ebner's) glands are also being studied, in order to determine the localization of secretory enzymes, particularly lipase, and the development of the secretory capabilities of the serous cells of the rat tongue.